Change Map binding behavior in ConfigProxy

The ConfigProxyFactory currently attempts to bind a Map to multiple properties where the key is the next name part of a property prefix and the value maps to one or more properties. This implementation turned out to be very error-prone and confusing to use.

The new behavior (which is consistent with Version 1) maks binding to Maps just like all other collections where the Map is parsed from a single property value with the format k1=v1,k2=v2,....